Conventional internal combustion engines used in automobiles and similar vehicles include a spin-on oil filter assembly for cleaning the motor oil. However, due to the fact that the conventional oil filter assembly only effectively removes particles of size 10 microns and larger, after some period of time smaller particles build up in the engine oil and require that the engine oil be replaced. Typical engine oil, and oil filter, replacement schedules are every 3,000 miles or three months, whichever occurs first.
It is known in certain types of vehicles, such as large trucks, to use an auxiliary bypass filter for additional filtering. A typical bypass filter retrofits to the truck engine where it diverts oil through a finer auxiliary filter element at a slower flow rate than the normal oil filter (e.g. 2.5 gallons per minute or less versus about 20 to 40 gallons per minute). Passing the engine oil through the auxiliary filter element aids in filtering out particles smaller than about 40 microns in size, thereby improving engine oil life as well as the life of the engine. Reference in this regard can be had to, for example, U.S. Pat. No. 5,552,065, Meddock et al.
However, this type of filtering arrangement is not typically suitable for use with automobiles and similar types of vehicles. A first issue relates to the difficulty in retrofitting a bypass oil filter assembly to the engine. In many cases there may simply not be room to mount the bypass oil filter assembly. A second issue relates to cost, as the use of the bypass oil filter assembly is inherently more costly than the use of only the conventional type of oil filter assembly.
As can be appreciated, there is a significant body of prior art that has been built up over the decades relating to oil filters and related techniques for internal combustion engines. Representative of this prior art are the following U.S. Patents.
In U.S. Pat. No. 3,986,960, Wire et al., describe a fluid filter containing a tubular canister having a contaminated fluid inlet and a filtered fluid outlet. The filter includes a solid tube forming a vertical central conduit within the canister and a plurality of axially space-apart containers mounted serially along the tube. Filtering material is located in the canisters. Ports in the tube communicate with chambers formed between the filter element and the bottom of the container. A seal is effected between the outlet of the canister and the tube, while fluid communication is provided between the inlet and the open tops of the containers such that fluid flow occurring between the inlet and the outlet takes place through the filter elements.
In U.S. Pat. No. 4,048,071, Yamada et al. describe a liquid filtering device where the peripheral surface of a coil of a filter web wound about a hollow shaft is covered by a liquid-impervious flexible coating, and the outer periphery of a first end of the coil is secured to a supporting disc so that when liquid to be filtered is caused to pass through the coil in the axial direction of the coil, the convolutions of the coil near a second end expand radially outwardly to trap contaminants in the spiral gap. Purified liquid collected at the first end of the coil is discharged through the hollow shaft. The filter unit is constructed such that a number of unites can be connected in series.
In U.S. Pat. No. 4,738,776 Brown describes a lubricant filter assembly for an internal combustion engine that includes a head member removably mounted on a base member. The head member includes a sleeve-like housing open at one end and having first and second filter units fixedly mounted therein. The outer peripheries of the filter units coact with the interior surface of the housing to form a common inlet passage. One of the filter units is provided with an interior first outlet passage which communicates with a first passage formation formed in the base member. The first passage formation communicates with a first lubricating circuit of the engine. The second filter unit is provided with an interior second outlet passage which communicates with a second passage formation formed in the base member. The second passage formation communicates with a second lubricating circuit of the engine. Seal sections are carried by the head member. One seal section effects a sealing engagement between the base member and a portion of the housing defining the open end. A second seal section is disposed within the housing and prevents direct communication between the inlet passage and the first outlet passage. A third seal section is disposed within the housing and prevents communication between the first and second outlet passages. The sealing engagement effected by the third seal section is enhanced upon the flow pressure within the interior first outlet passage being increased.
In U.S. Pat. No. 5,178,753 Trabold describes an oil filter for internal combustion engines that is used in a secondary oil circuit in addition to a conventional oil filter. The oil filter includes a filter housing in which a filter element consists of a roll of absorbent paper that is wound about a rod. The oil filter is configured as a set of elements that comprises body sections and caps, and a rod with the rolled filter element. The volume of the oil filter can be matched to a particular application by connecting a plurality of body sections with an appropriate number of rods.
In U.S. Pat. No. 5,556,543 Trabold describes an oil filter for internal combustion engines. The oil filter includes a filter housing and a filter packing made of a porous deformable material, e.g., a roll of absorbent paper. To prevent the filter packing from being deformed and thereby preventing a smooth flow through the filter packing, stabilizing elements, e.g., stabilizing bars, are provided for fixing the form and position of the filter packing within the filter housing.
A long-felt and unfulfilled need exists to provide an oil filter assembly for an internal combustion engine that provides, within a conventionally-sized oil filter container, a conventional oil filter and a bypass oil filter capable of entrapping and thus removing smaller particles from the oil than the conventional oil filter.
Prior to this invention, this need was not adequately fulfilled by the prior art filter assemblies and methods that are known to the inventor.